Denny, in the book I mentioned, the tell you under water is safer than under beer. Again, I have no experience in this and I am looking for guidance.
The practice outlined on page 168 of Yeast goes against what is practiced by the professional brewing community and most of the long-time veterans in the amateur brewing community. In fact, the practice contradicts what Chris White wrote for BrewPub magazine, which leads to me to believe that the yeast rinsing section was a Jamil addition. http://www.probrewer.com/library/archives/keeping-your-yeast-healthy-longer/
Yeast is a living organism and is most happy and healthy when feeding on wort sugars. When fermentation is complete, yeast cells flocculate to the bottom of the fermenter. They then go into a resting state. Yeast under beer is fairly stable, and most brewers agree that the best place to store yeast is under beer. But two crucial factors are temperature and time.
The problem with the yeast rinsing section of the book is that many home brewers have misinterpreted what was written. The authors offered the technique as a method to select yeast cells. Here's the first paragraph from that section:
The question many homebrewers have is, "How do I select only the best yeast if harvesting the entire contents of the fermentor?" The answer lies in yeast rinsing. While it cannot replace selecting the ideal yeast with a shovel, it can help separate out the trub, dead cells, and alcohol from your pitch.
There are other ways to select the best cells that do not involve the possibility of contaminating one's culture. I outlined a process that many amateur brewers use to bottom crop relatively trub and dead cell free yeast without exposing the culture to boiled water in the thread linked in my signature.
The authors go onto attempt to justify a risk-laden process in commercial settings.
Rinsing can also be worthwhile in commercial settings, especially for yeast harvested from a high-gravity beer.
Green beer, while toxic to domesticated yeast, is even more toxic to house microflora. Green beer also contains non-fully digested sources of carbon. Sugar belongs to a class of substances known as carbohydrates. Carbohydrates are compounds made of carbon bound to water (i.e., hydrated carbon). All the sugars found in wort break down into multiples of CH2
O. The simplest sugars found in wort are known as hexoses because they contain six carbon atoms. The most common hexose is glucose. Hexoses have the chemical formula C6
. Ethanol is also source of carbon. It has the chemical formula C2
O (or CH3
OH). Under the right conditions, yeast will consume ethanol via a metabolic process known as diauxic shift.
Finally, here's something that Fermentis wrote about storing yeast out of beer:http://www.fermentis.com/wp-content/uploads/2010/07/2010_TT_EN_HD.pdf
In case of repitching, yeast must not be stored out of beer for long periods, even at low temperatures, as yeast
glycogen levels will fall causing slow fermentations.
Fementis' parent company, Lesaffre, is a multi-national yeast and fermentation powerhouse. Their yeast research spans brewing to yeast lines used in health-related research. If you perform a Google search using the terms "Lesaffre" and "bioreactor," you will see that Fermentis is just a drop in the Lesaffre yeast bucket.